The first goal of this project is to systematically evaluate the impact of our initial data that MIB-1 labeling indices (LI) of focal regions of proliferation in grade Il astrocytomas predict patient survival. Patients with this neoplasm have a wide range of survivals despite the same histopathologic features of their tumors, confounding prediction of outcome by the neuropathologist. MIB- l is a new genetically engineered marker of cellular proliferation that recognizes Ki-67 epitopes in paraffin sections of archival tissue. In a recent study of grade Il astrocytomas, sampling focal regions of highest proliferation labeled by MIB-1 in each astrocytoma maximized its predictive power. We will evaluate whether this predictive value of MIB- l discovered at the University of Michigan Medical Center is relevant to other groups of grade Il astrocytoma patients from different racial backgrounds and hospital environment. This evaluation will be enhanced by collaborations with other institutions, and by new collaborations with cooperative cancer study groups. The predictive power of MIB- l LI will be compared with other clinical and prognostic factors including age, gender, symptoms, and treatments. The effects on predictive capabilities of these factors including MIB- l of recent change in World Health Organization (WHO) classification systems will be accessed. Although their average survival is less than grade Il astrocytoma patients grade III anaplastic astrocytoma patients have a wide range of outcomes. Our second goal will be to evaluate the predictive power of MIB- l to differentiate long and short survivors in this single histopathologic category. The analytical approach and strategy to pursue positive results will be the same as described above. Finally, the effects of sampling on histopathologic grading and on MIB-l LI will be assessed.